1. Field of the Invention
The present invention relates to a method for manufacturing a semiconductor device by using droplet discharge typified by ink-jet.
2. Description of the Related Art
In manufacture of semiconductor devices, the use of droplet discharge has been examined for development of producing technologies by which a plurality of display panels is taken from one mother glass substrate for efficient mass production.
In order to form a film pattern for a conventional semiconductor device, a method for forming a film pattern is used, where a film (a film comprising a semiconductor material, an insulator material, or a conductive material) at a portion to be the film pattern is removed by etching with a resist pattern as a mask pattern after a photolithography process of forming the resist pattern by applying a resist on the whole area of a substrate, pre-baking the applied resist, and then, irradiation with light such as ultraviolet through a photomask and development of the irradiated resist.
On the other hand, in order to improve current-voltage characteristics, that is, driving ability, by increasing drain current of a TFT in a linear region and saturation region, for example, the electron mobility is improved, the capacitance of a gate insulating film is increased, and the ratio of a channel width to a channel length (hereinafter, referred to as W/L) is increased (refer to Patent Reference 1).
(Patent Reference 1) Japanese Patent Laid-Open No. 2000-275678
However, the process of forming a film pattern by using the conventional photolithography process has problems that most of the materials of the film pattern and resist are wasted and the number of processes for forming the mask pattern is large to decrease the throughput.
As one of methods for increasing W/L in order to improve current-voltage characteristics of a TFT, a method of expanding the channel width (W) can be given. However, this structure has a problem that the area of the TFT is increased. In the case of using a TFT as a switching element for a pixel of a transmissive display device, there are one or more TFTs in a pixel of a display portion. Therefore, the increase of the area of the TFT has a problem that the display region of the pixel region is limited to decrease the aperture ration of the display device.
In addition, as another method for increasing W/L, a method of reducing the channel length (L) can be given. However, in order to reduce the channel length (L) with the use of a droplet discharge system, it is necessary that a solution that has a small droplet size be discharged with the use of a small discharge nozzle in diameter to form a film pattern (a gate electrode or source and drain regions). However, in the case of a droplet discharge system that has a small discharge nozzle in diameter, the composition of a discharge solution adheres the tip of the discharge nozzle, dries, and solidifies to cause clogging makes it difficult to discharge a specific amount of discharge solution continuously and stably. Consequently, the method using the droplet discharge system has a problem that decrease in throughput and yield is caused.